5 files changed, 37 insertions, 11 deletions

diff --git a/sound/usb/line6/capture.c b/sound/usb/line6/capture.c
index 0228cb4bdfcf..7c812565f90d 100644
--- a/sound/usb/line6/capture.c
+++ b/sound/usb/line6/capture.c
@@ -232,6 +232,8 @@ static int snd_line6_capture_open(struct snd_pcm_substream *substream)
         if (err < 0)
                 return err;
 
+        line6_pcm_acquire(line6pcm, LINE6_STREAM_CAPTURE_HELPER, false);
+
         runtime->hw = line6pcm->properties->capture_hw;
         return 0;
 }
@@ -239,6 +241,9 @@ static int snd_line6_capture_open(struct snd_pcm_substream *substream)
 /* close capture callback */
 static int snd_line6_capture_close(struct snd_pcm_substream *substream)
 {
+        struct snd_line6_pcm *line6pcm = snd_pcm_substream_chip(substream);
+
+        line6_pcm_release(line6pcm, LINE6_STREAM_CAPTURE_HELPER);
         return 0;
 }
 
diff --git a/sound/usb/line6/driver.h b/sound/usb/line6/driver.h
index 2d3213912d4c..0bcab38ac10d 100644
--- a/sound/usb/line6/driver.h
+++ b/sound/usb/line6/driver.h
@@ -100,8 +100,10 @@ enum {
         LINE6_CAP_CONTROL =     1 << 0,
         /* device supports PCM input/output via USB */
         LINE6_CAP_PCM =         1 << 1,
-        /* device support hardware monitoring */
+        /* device supports hardware monitoring */
         LINE6_CAP_HWMON =       1 << 2,
+        /* device requires output data when input is read */
+        LINE6_CAP_IN_NEEDS_OUT = 1 << 3,
 };
 
 /*
diff --git a/sound/usb/line6/pcm.c b/sound/usb/line6/pcm.c
index a5a44309bc9d..fab53f58d447 100644
--- a/sound/usb/line6/pcm.c
+++ b/sound/usb/line6/pcm.c
@@ -52,7 +52,7 @@ static int snd_line6_impulse_volume_put(struct snd_kcontrol *kcontrol,
 
         line6pcm->impulse_volume = value;
         if (value > 0) {
-                err = line6_pcm_acquire(line6pcm, LINE6_STREAM_IMPULSE);
+                err = line6_pcm_acquire(line6pcm, LINE6_STREAM_IMPULSE, true);
                 if (err < 0) {
                         line6pcm->impulse_volume = 0;
                         return err;
@@ -242,6 +242,14 @@ int snd_line6_trigger(struct snd_pcm_substream *substream, int cmd)
                 switch (cmd) {
                 case SNDRV_PCM_TRIGGER_START:
                 case SNDRV_PCM_TRIGGER_RESUME:
+                        if (s->stream == SNDRV_PCM_STREAM_CAPTURE &&
+                                (line6pcm->line6->properties->capabilities &
+                                        LINE6_CAP_IN_NEEDS_OUT)) {
+                                err = line6_stream_start(line6pcm, SNDRV_PCM_STREAM_PLAYBACK,
+                                                 LINE6_STREAM_CAPTURE_HELPER);
+                                if (err < 0)
+                                        return err;
+                        }
                         err = line6_stream_start(line6pcm, s->stream,
                                                  LINE6_STREAM_PCM);
                         if (err < 0)
@@ -250,6 +258,12 @@ int snd_line6_trigger(struct snd_pcm_substream *substream, int cmd)
 
                 case SNDRV_PCM_TRIGGER_STOP:
                 case SNDRV_PCM_TRIGGER_SUSPEND:
+                        if (s->stream == SNDRV_PCM_STREAM_CAPTURE &&
+                                (line6pcm->line6->properties->capabilities &
+                                        LINE6_CAP_IN_NEEDS_OUT)) {
+                                line6_stream_stop(line6pcm, SNDRV_PCM_STREAM_PLAYBACK,
+                                          LINE6_STREAM_CAPTURE_HELPER);
+                        }
                         line6_stream_stop(line6pcm, s->stream,
                                           LINE6_STREAM_PCM);
                         break;
@@ -283,14 +297,15 @@ snd_pcm_uframes_t snd_line6_pointer(struct snd_pcm_substream *substream)
         return pstr->pos_done;
 }
 
-/* Acquire and start duplex streams:
+/* Acquire and optionally start duplex streams:
  * type is either LINE6_STREAM_IMPULSE or LINE6_STREAM_MONITOR
  */
-int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int type)
+int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int type, bool start)
 {
         struct line6_pcm_stream *pstr;
         int ret = 0, dir;
 
+        /* TODO: We should assert SNDRV_PCM_STREAM_PLAYBACK/CAPTURE == 0/1 */
         mutex_lock(&line6pcm->state_mutex);
         for (dir = 0; dir < 2; dir++) {
                 pstr = get_stream(line6pcm, dir);
@@ -300,10 +315,12 @@ int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int type)
                 if (!pstr->running)
                         line6_wait_clear_audio_urbs(line6pcm, pstr);
         }
-        for (dir = 0; dir < 2; dir++) {
-                ret = line6_stream_start(line6pcm, dir, type);
-                if (ret < 0)
-                        goto error;
+        if (start) {
+                for (dir = 0; dir < 2; dir++) {
+                        ret = line6_stream_start(line6pcm, dir, type);
+                        if (ret < 0)
+                                goto error;
+                }
         }
  error:
         mutex_unlock(&line6pcm->state_mutex);
diff --git a/sound/usb/line6/pcm.h b/sound/usb/line6/pcm.h
index 67fda315aa89..bb0c9cbf2a78 100644
--- a/sound/usb/line6/pcm.h
+++ b/sound/usb/line6/pcm.h
@@ -73,6 +73,7 @@ enum {
         LINE6_STREAM_PCM,
         LINE6_STREAM_MONITOR,
         LINE6_STREAM_IMPULSE,
+        LINE6_STREAM_CAPTURE_HELPER,
 };
 
 /* misc bit flags for PCM operation */
@@ -191,7 +192,8 @@ extern int snd_line6_hw_params(struct snd_pcm_substream *substream,
 extern int snd_line6_hw_free(struct snd_pcm_substream *substream);
 extern snd_pcm_uframes_t snd_line6_pointer(struct snd_pcm_substream *substream);
 extern void line6_pcm_disconnect(struct snd_line6_pcm *line6pcm);
-extern int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int type);
+extern int line6_pcm_acquire(struct snd_line6_pcm *line6pcm, int type,
+                               bool start);
 extern void line6_pcm_release(struct snd_line6_pcm *line6pcm, int type);
 
 #endif
diff --git a/sound/usb/line6/toneport.c b/sound/usb/line6/toneport.c
index da76e030eefc..8e22f430d700 100644
--- a/sound/usb/line6/toneport.c
+++ b/sound/usb/line6/toneport.c
@@ -177,7 +177,7 @@ static int snd_toneport_monitor_put(struct snd_kcontrol *kcontrol,
         line6pcm->volume_monitor = ucontrol->value.integer.value[0];
 
         if (line6pcm->volume_monitor > 0) {
-                err = line6_pcm_acquire(line6pcm, LINE6_STREAM_MONITOR);
+                err = line6_pcm_acquire(line6pcm, LINE6_STREAM_MONITOR, true);
                 if (err < 0) {
                         line6pcm->volume_monitor = 0;
                         line6_pcm_release(line6pcm, LINE6_STREAM_MONITOR);
@@ -246,7 +246,7 @@ static void toneport_start_pcm(unsigned long arg)
         struct usb_line6_toneport *toneport = (struct usb_line6_toneport *)arg;
         struct usb_line6 *line6 = &toneport->line6;
 
-        line6_pcm_acquire(line6->line6pcm, LINE6_STREAM_MONITOR);
+        line6_pcm_acquire(line6->line6pcm, LINE6_STREAM_MONITOR, true);
 }
 
 /* control definition */